<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <img src="../img/1.jpg" alt="">
    <script>
        const random = Math.floor(Math.random() * 3) + 1
        const img = document.querySelector('img')
        //修改标签属性
        img.src = `../img/${random}.jpg`
    </script>
</body>

</html>